Thick film heating elements refer to heating elements that are made by fabricating exothermic materials on a substrate thick films and providing electricity to generate heat. The conventional heating methods include electrical heating tube heating and PTC heating. An electrical heated tube heating element uses a metal tube as the outer case and distributes spirally nickel-chromium or iron-chromium alloy spirally therein to form heater strips; the clearance space is then filled with magnesite clinker that has excellent thermal conductivity and insulativity and sealed with silica gel from two ends of the tube. The PTC heating method uses ceramics as the exothermic material. Both electrical heated tube heating and PTC heating conduct heating indirectly with low thermal efficiency, and are structurally huge and bulky. Besides, in consideration of environmental protection, heaters using these two types of heating methods stain easily after repeatedly heating and cleaning thereof is not easy. Additionally, PTC heaters contain lead and other hazardous substances and are easily oxidized, causing power attenuation and short service life.
Chinese application CN201210320614.9 discloses an aluminum alloy heating tube using thick film heating, which comprises a heating tube body and a thick film heating plate. An insertion slot, the depth direction of which extends radially inward, is disposed at a side of the heating tube body. The thick film heating plate is positioned in the insertion slot. The heating tube body has through-holes, the length direction of which exten axially inward along the heating tube body, disposed on two sides of the insertion slot. In the aluminum alloy heating tube, the thick film heating circuit on the thick film circuit board is printed on the ceramics substrate or a substrate of other insulating material. In addition, the thick film circuit board is coated with one more layer of insulating medium; therefore, the surface of the entire thick film circuit board is insulative.
Chinese application CN201010110037.1 discloses a thick film heating assembly with dry burning protection function, which comprises a thick film heater for electrical heating, an electrical connection bracket mounted on the thick film heater for connecting the thick film heater with external components, and a dry-burning protector mounted on the thick film heater. The electrical connection bracket and the dry-burning protector form the whole components, and the dry-burning protector contains at least one electrical dry-burning-proof protector electrically connected to the control circuit and one mechanical dry-burning-proof protector.
Although the existing heating elements have gradually been applied to the field of household electrical appliances, the heating bodies of the thick film element mentioned above are attached onto the electrical appliances, and few independent components are existed at present. Up to date, none of the existing heating elements has double-sided high heat conductivity, and no double-sided heating thick film element has been applied to daily living and industrial production to realize the function of uniform heating on both sides of the element.